Multiple axis vibration test platform

Abstract

A multiple axis vibration test platform including a plurality of actuator arms connected to respective drive shafts with eccentric ball joints at first ends thereof, and at the opposite ends thereof to the bottom surface and side walls of the test platform with concentric ball joints. The eccentricity of the eccentric ball joint couplings correspond to the amplitude of vibration of the test platform along a respective axis of vibration. The ball joint couplings at each end of the actuator arms eliminate cross coupling of motion between the axes of vibration as the test platform is vibrated simultaneously in more than one axis.

What is claimed is: 
     
       1. A multi-axis vibration test platform, comprising: a test platform having a top surface, a bottom surface, side walls, and end walls, said platform being simultaneously movable along selected ones of first, second, and third axes of vibration which intersect at a center of said test platform;   a plurality of actuator arms having first and second ends;   a plurality of rotatable drive shafts and means for independently rotating each of said drive shafts;   first means, including eccentrically coupled ball joints, for connecting said first end of each said actuator arm to a respective one of said plurality of drive shafts to reciprocate each said actuator arm along a respective one of said axes in accordance with the eccentricity of said eccentrically coupled ball joint as said respective drive shaft is rotated;   second means, including concentrically coupled ball joints, for connecting said second end of each said actuator arm to a respective one of said bottom surface, side walls, and end walls of said test platform, said concentrically mounted ball joints permitting out of axis rotation of said actuator arms relative to said test platform.   
     
     
       2. The multi-axis vibration test platform of claim 1, wherein each said rotatable drive shaft includes at least two of said plurality of actuator arms extending therefrom, said eccentrically coupled ball joints of said first connecting means of said first ends of said at least two actuator arms being spaced apart on each said rotatable drive shaft on opposite sides of a respective one of said axes to restrict rotation of said test platform about said respective axis. 
     
     
       3. The multi-axis vibration test platform of claim 2, wherein each one of said rotatable drive shafts is aligned in parallel with a respective one of said first, second, and third axes of vibration of said test platform with said at least two actuator arms of each said rotatable drive shaft extending perpendicularly therefrom. 
     
     
       4. The multi-axis vibration test platform of claim 3, wherein said first, second, and third axes of vibration are orthogonal to one another. 
     
     
       5. The multi-axis vibration test platform of claim 2, wherein the eccentricity of said eccentrically coupled ball joints of said first connecting means corresponds to an amplitude of vibration of said test platform along a respective axis, and wherein the eccentricity of each said eccentrically coupled ball joint of said at least two actuator arms are disposed in substantially identical orientation with respect to one another and relative to said respective drive shaft. 
     
     
       6. The multi-axis vibration test platform of claim 1, wherein said eccentrically coupled ball joints include a socket formed in said first end of each said actuator arm, a ball pivotably held in said socket, and a cam rotatably held in said ball, said cam having a center and being fixedly attached to said respective drive shaft at a position offset from said center of said cam, said offset corresponding to said eccentricity of said eccentrically coupled ball joint. 
     
     
       7. The multi-axis vibration test platform of claim 6, including a bearing disposed between said cam and said ball. 
     
     
       8. The multi-axis vibration test platform of claim 1, wherein said concentrically coupled ball joints include a socket formed in said second end of each said actuator arm and a ball pivotably held in said socket, said ball including a centrally positioned hole extending therethrough; said second connecting means further including a hinge having a base portion, fixedly attached to a respective one of said bottom surface, side walls, and end walls of said test platform, and two spaced retaining portions extending perpendicularly from said base portion and parallel to one another, each said retaining portion having an aperture therethrough aligned with said centrally positioned hole of said ball, said ball being held between said retaining portions with an attachment bolt extending through said apertures and said centrally positioned hole. 
     
     
       9. The multi-axis vibration test platform of claim 8, including a bearing disposed between said ball and said socket. 
     
     
       10. The multi-axis vibration test platform of claim 8, wherein each said retaining portion includes means for aligning said hole of said ball and said apertures of said retaining portion and for limiting movement of said ball along said attachment bolt between said retaining portions. 
     
     
       11. The multi-axis vibration test platform of claim 10, wherein said aligning means includes tapered, self-centering elements positioned around said apertures on opposing surfaces of said retaining portions. 
     
     
       12. The multi-axis vibration test platform of claim 1, wherein said means for independently rotating each of said drive shafts includes a plurality of motors, operably connected to respective ones of said plurality of drive shafts. 
     
     
       13. The multi-axis vibration test platform of claim 12, including control means for activating and deactivating selected ones of said motors to rotate corresponding ones of said drive shafts and reciprocate said test platform along respective ones of said axes. 
     
     
       14. The multi-axis vibration test platform of claim 13, wherein said control means includes means for varying the frequency of rotation of each said drive shaft to adjust the frequency of vibration of said test platform along a respective one of said axes.